The new report says: "It is now clear - although we are still far from having established the truth - that authorities in several European countries actively participated with the CIA in these unlawful activities.

Although the Swiss senator says the US must bear responsibility for the flights, he says the programme could operate only with "the intentional or grossly negligent collusion of the European partners".

The "spider's web" of US rendition flights is based on an "utterly alien" approach that breaches human rights, he concludes.

'Black sites'

In Warsaw, Polish Prime Minister Kazimierz Marcinkiewicz described the latest accusations as "libellous", while Romania rejected them as "speculation".

COUNCIL OF EUROPE

Founded in 1949 and based in Strasbourg, France

Forty-six members, 21 of them from Central and Eastern Europe

Set up to defend human rights, parliamentary democracy and the rule of law

Acts as human rights watchdog for Europe

Oversees the European Court of Human Rights

Comprises a decision-making committee of ministers and 630-member parliamentary assembly

In London, Tony Blair said the report "added absolutely nothing new whatever to the information we have".

The BBC's Security correspondent, Frank Gardner, says that while the report makes uncomfortable reading for many European countries, the Council of Europe has been hampered by its lack of investigative powers.

The evidence in the report is largely circumstantial, our correspondent says, and proving many of the allegations, such as the existence of so-called "black sites", is beyond the Council's powers.

The report is intended to wake up Europe's conscience to get national parliaments to investigate properly, our correspondent concludes.

Torture denial

Media allegations on CIA jails broke last November, when the Washington Post newspaper said the intelligence agency had been running facilities in eastern Europe, Afghanistan and Thailand.

It said more than 100 people had been sent to facilities known as "black sites" since they were set up following the 11 September 2001 attacks.

European media reports have since alleged that the CIA has used several European airports for its programme of "extraordinary renditions".

Under the highly secretive process, US intelligence agencies send terror suspects for interrogation by security officials in other countries, where they have no legal protection or rights under American law.

Washington does not deny that terror suspects have been transferred for interrogation in other countries, but rejects accusations that they are being tortured.